Echocardiography in the Intensive Care Unit

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Echocardiography has evolved to become a widely used and versatile modality for diagnosis and monitoring of critically ill patients. As such, its use has expanded from the cardiology suite into the emergency room, peri-operative period, and intensive care unit (ICU). Echocardiography provides both anatomical and functional information about the heart, with the ability to assess systolic and diastolic function, cavity size, and valvular function.1


Basic Terminology of Echocardiography Techniques
In order to reach a diagnosis or decide on a management plan, a sonographer must utilize different echocardiographic imaging techniques and hemodynamic modalities. The following is a list of the basic techniques used during an echocardiographic study.

2D Echocardiography
2D echocardiography is the backbone of the echocardiographic exam.2 Using 2D, a complete visualization of the beating heart is achieved by displaying anatomical structures in realtime tomographic images. By aiming the ultrasound probe at the heart, precisely oriented anatomical ├óÔé¼´åİslices™ are obtained. The information acquired includes cardiac chamber size, global and regional systolic function, and valvular anatomy.

M-mode Echocardiography
M-mode or motion-mode images are a continuous 1D graphic display that can be derived by selecting any of the individual sector lines from which a 2D image is constructed.2 It is useful for quantification of myocardial wall and chamber sizes, which in turn can be used to estimate left ventricular (LV) mass and chamber volume, respectively. In addition, since it has high temporal resolution, M-mode is helpful in assessing the motion of rapidly moving cardiac structures such as cardiac valves.

Doppler Echocardiograph
Doppler echocardiography is used to supplement 2D and M-mode echocardiography. It can provide functional information regarding intra-cardiac hemodynamics: systolic and diastolic flow, blood velocity and volume, severity of valvular lesions, location and severity of intracardiac shunts, and assessment of diastolic function. The four types of Doppler modality used are continuouswave (CW), pulsed-wave (PW), color flow mapping (CFM), and tissue Doppler.2 CW Doppler is used for measuring high-pressure-gradient/high-velocity flows, such as those seen in aortic stenosis. When using CW Doppler, the ultrasound probe continuously transmits and receives sound waves. CW Doppler can evaluate higher flows, but does so at the expense of spatial specificity. PW Doppler is used for measuring lower-pressure-gradient/lower-velocity flows, such as those seen in mitral stenosis. In this mode, the ultrasound probe sends out a pulse of sound and then waits to receive reflected waves. CFM is useful for screening valves for stenosis or regurgitation, quantifying the degree of valvular regurgitation, imaging systolic and diastolic flow, and detecting intracardiac shunts.


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